The present invention relates to a medical pump and, more particularly, to an ambulatory infusion pump.
Oftentimes, medical patients require precise delivery of continuous medication or at set periodic intervals. Certain liquid medicaments, or drugs, however, rarely achieve their maximum therapeutic action through conventional injection techniques. And, many drugs reach their full potential only through precise delivery over an extended period of time. Medical pumps have been developed to provide controlled drug infusion through the pump wherein the drug can be administered at a precise rate that keeps the drug concentration within the therapeutic margin and out of a possible toxic range with certain drugs. The medical pumps provide appropriate drug delivery to the patient at a controllable rate which does not require frequent medical attention. The medical pumps further facilitate administration of intravenous therapy to patients outside of a clinical setting. In addition, doctors have found that in many instances patients can return to substantially normal lives, provided that they can receive periodic or continuous intravenous administration of medication. These factors have combined to promote the development of increasingly lightweight, portable or ambulatory infusion pumps that can be worn by a patient and are capable of administering a continuous supply of medication at a desired rate.
A wide variety of ambulatory pumps in use in the medical field are intended to meet the need of a high degree of accuracy in the administration of fluids to maximize the effectiveness of medication and to protect the patient. Typically, these ambulatory infusion pumps include a pump control unit and a drive mechanism including a variety of operating controls adapted to accept a disposable pump chamber assembly. The pump chamber assembly has an inlet end connected to a liquid reservoir and an outlet end connected to an I.V. tube that in turn is connected for intravenous administration to a patient by a cannula.
Often, the same medical pump is programmable to allow for different pump application programs for pumping different therapeutics to a patient, such as antibiotic therapy, chemotherapy, pain control therapy, and nutritional therapy, etc. With regard to pain control therapy, medical infusion pumps are typically used for the management of acute pain, frequently in a hospital setting. These pumps deliver morphine or other analgesics to the patient, according to a pre-programmed prescription controlled by the pump. These pumps generally include various modes of infusion, such as a continuous mode in which the liquid medicament is continuously infused at a constant rate, or a ramp mode in which the rate of infusion gradually increases, then remains constant, and then gradually decreases. Further, these pumps include the capability for patient demand dosing. Typically, pain control therapy utilizing pumps having patient demand dosing capabilities is referred to as xe2x80x9cPCAxe2x80x9d or patient controlled analgesia.
With PCA, it is critical to carefully track the amount of drug a patient has received, the number of times the patient has requested additional demand doses, and the number of demand doses actually delivered to the patient, along with other information. Such historical information is utilized to adjust or xe2x80x9ctitratexe2x80x9d the patient""s prescription. For such purposes, PCA infusion pumps have a non-volatile memory in which infusion parameters may be stored and from which such parameters may be retrieved. U.S. Pat. No. 5,181,910 discloses an infusion pump that is programmable and has an integral controller for automatically controlling and determining the interval between pump activations necessary to produce a substantially linear rate of increase or decrease in liquid flow during the administration of liquid medicament to a patient. The integral controller is a keypad on the face of the pump having keys which a clinician manually depresses to program the pump. These pumps also have a non-volatile memory in which such pump-specific infusion parameters may be stored and from which such parameters may be retrieved.
Typical parameters that these pumps, which have integral processors or controllers, are able to control include: the rate at which the medicament is infused, the volume or dosage of medicinal fluid administered, whether the drug is delivered as a bolus or continuous infusion, the time that the administration occurs, and/or the interval of time that the pump will operate. These parameters are usually entered into the electronic non-volatile memory of the pump controller via a user interface control panel on the pump (i.e., a keypad on the face of the pump). Although entry of the pump-specific parameters that control the pump""s operation may be relatively straightforward, several minutes may be required to specify all of the data required to define a drug delivery protocol. More important, each time that a pump is programmed to administer a specific medicinal fluid, there is a risk that human error may cause improper values for the parameters to be entered.
In addition to historical xe2x80x9cpump-specificxe2x80x9d information, additional xe2x80x9cpatient-specificxe2x80x9d information is required for the patient""s medical chart. Thus, adequate monitoring of the drug pump and the patient""s usage of the drug pump, along with monitoring of the patient, is still required. The combination of infusion data (i.e., xe2x80x9cpump-specificxe2x80x9d information) and patient data (i.e., xe2x80x9cpatient-specificxe2x80x9d information) is necessary to generate a complete historical record or patient chart.
U.S. Pat. No. 5,795,327, owned by the Assignee of the present invention, discloses an infusion pump with historical data recording capabilities. The pump includes a controller integral with the pump to cause the pump to deliver a plurality of infusions of liquid medicament during the infusion period, each of the infusions being made at a specific time period and flow rate, and a keypad to allow a clinician to input the program parameters into the pump. The apparatus has a nonvolatile memory and means for storing infusion data in the non-volatile memory to generate a complete historical record of the xe2x80x9cpump-specificxe2x80x9d data including data regarding the infusions delivered during the infusion period. The xe2x80x9cpump-specificxe2x80x9d infusion data stored in the non-volatile memory may include programmed infusion data manually inputted to the infusion apparatus by a clinician during programming of the apparatus through the integral keypad controller. Such manually programmed infusion data may include data representing the infusion mode, the infusion flow rate, the volume to be infused, and the infusion start time. The infusion data may also include resulting data, including data representing the time at which each infusion was made during the infusion period and the flow rate at which of each infusion was made.
In addition to storing infusion data, the pump automatically records additional real-time infusion data (i.e., more xe2x80x9cpump-specificxe2x80x9d information). Such data includes the times at which the run and hold keys of the pump to control the infusion were pressed by the user, the time at which the bolus-request key was pressed, including bolus requests for PCA demand dosing, whether the bolus infusion was made as requested, the time at which any alarms or malfunctions occurred, data representing the type of alarm or malfunction, and data relating to the infusion modes which were locked out, if such means are available.
Automatic recording of the xe2x80x9cpump-specificxe2x80x9d infusion data described above in the non-volatile memory during the manual programing and operation of the infusion apparatus allows the operator to generate a historical data record of the apparatus. This data can later be retrieved from the non-volatile memory and used for various purposes, including clinical purposes, and to confirm that the prescribed infusion was actually delivered.
Additionally, U.S. Pat. No. 5,795,327 discloses the ability of the pump to present the patient with a plurality of questions to be answered by the patient. The questions are displayed on a screen on the face of the pump, and the answers are input through the keypad on the face of the pump adjacent the display. The answers are stored in the pump""s non-volatile memory. Typically, the questions may be related to the current health of the patient, and/or to the patient""s health history. The infusion apparatus may have a non-volatile memory in which a plurality of question sets are stored, and the questions asked of the patient may be taken from one of the question sets which is selected based on a parameter relating to the type of infusion the patient is to receive, or has just received. These question sets are manually inputted into the infusion apparatus by a clinician during programming of the apparatus through an integral keypad on the pump.
Many concerns arise in connection with the operation of the drug pumps and with the collection and merging of data to produce a complete and accurate patient chart. One concern arises in the monitoring of the drug pump. Another concern arises in monitoring the accurate running of the software stored in the pump. Another concern arises in loading and controlling the different pump application programs for operating the pump. Another concern arises in obtaining data feedback from the drug pump. Another concern arises in communicating the data feedback from the drug pump to the patient""s chart. Another concern arises in merging pump is data with patient-specific data.
Additional concerns arise in controlling the size and weight of the ambulatory infusion pump. As discussed, the pump must be lightweight and portable as it is designed to be worn by a patient. By wearing the pump, the patient can achieve as close to a normal lifestyle as possible while still receiving a supply of medicament as needed. Accordingly, size and weight of the pump are important. Certain syringe-based pumps have been developed for use as ambulatory infusion pumps. The syringe-based pumps require an external linkage such as a plunger rod that is connected to a plunger within the syringe. It is necessary for the plunger rod to be at least as long as the fluid chamber of the syringe so that the syringe can be completely evacuated. The linkage requires a drive mechanism positioned outside of the syringe to move the plunger. In addition, a larger case is required to house the syringe, external linkage and associated power sources. These additional components add to the overall size and weight of the pump. Yet another concern is precisely controlling the infusion rate of the pump.
The present invention is provided the solve these and other problems.
The present invention provides an ambulatory infusion pump that, in a preferred embodiment, is a syringe-based ambulatory infusion pump. The pump has a syringe having a unique self-propelled infusion engine that displaces fluid from the syringe and into an ambulatory patient.
According to one aspect of the present invention, the ambulatory infusion pump has a syringe barrel having a fluid chamber and an inner wall. The pump further has an infusion engine for moving fluid through the syringe barrel. The engine has a member for engaging a portion of the syringe barrel for moving the engine linearly along the syringe barrel.
According to another aspect of the invention, the engine is positioned entirely within the syringe barrel.
According to a further aspect of the invention, the member engages the inner wall to move the engine linearly along the syringe barrel. The member is a tine and generally comprises a plurality of circumferentially spaced tines.
According to a further aspect of the invention, the fluid chamber has a first length and the engine has a second length wherein the second length is less than the first length.
According to yet another aspect of the invention, a method is disclosed for infusing a fluid to a patient. A syringe barrel is provided having a fluid chamber and an infusion direction. An infusion engine is also provided having a member for engaging a portion of the syringe barrel. The infusion engine is positioned within the fluid chamber. The engine is driven linearly within the fluid chamber by moving the member into operative engagement with a portion of the syringe. To drive the engine, a first portion of the infusion engine is moved in the infusion direction while a second portion remains stationary to define an infusion cycle. The second portion is then moved while the first portion remains stationary to define a reset cycle.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.